OUR ADVERTISERS

Tuesday, August 08, 2006

REMOVING THE ONE PIECE CRANK FROM THE FRAME

Most coaster brake bikes are equiped with what is called a one piece crank bottom bracket. They can also be found on BMX bikes and the cheap variety chain store bikes. This set-up is pretty heavy compared to the three piece bottom bracket, but it has the advantage of being pretty tough with its washing machine type crown bearings. I've opened up bikes that the bearings had never seen the light of day for 30 years and still find them in working order. Also, I've never seen a one piece crank break or come off.

Our Lowrider project is equiped with such a bottom bracket and we are going to take it off. Pretty easy if you follow my step by step illustrations. One thing to remember is that some threads are reversed on a bike, like the left side pedal and the locknut and bearing cone on the left side of the bottom bracket. You have to unscrew those by going clockwise.

After you've taken everything apart, make sure you store it all in a place you can find it again and not lose anything throughout the cleaning process before reassembly. Our next article will be about how to clean out all these nice parts. Until then, ride safe.

My sons pedals on his bmx bike wont turn his wheel? It is a free-agent bike with a crank like the one described here? Do you think its the crank that has something broken or the back tire which has a small sproket on it? Something is not engaging? Can you help?

I too, am a big fan of 1 piece cranks on most things, except BMX. I snapped one on my BMX, and went to a 3 piece. Never looked back. Then again, I wreck a lot of chains, freewheels and the like. My cruiser, however, does just fine with the double-bender.

Heather, the left side pedal(the side without the chain) as to be turned clockwise to unscrew it, the right pedal unscrews normally counterclockwise. If it's stuck, use a hammer on the wrench but be careful. The CCM Scrambler was made in the late 60's.

Freaking awesome walk through! Bought a great old racer cheap last year. Any other place but NYC it would have been free. Thing weighs five thousand pounds:) Striped it down and cleaned almost everypart(first time in 20 years I think!), got it ready for touring, and bounced around Maine for four weeks.

Untill reading your walkthrough and seeing the pictures today the ONLY place I did not know how to get at was inside the crank area to clean and grease the barrings.

I just finished opening and cleaning my on piece crank and wanted to say thanks!!

Update.Went on the first big bike ride today after playing with the crank. After about 7 miles I found myself trying to put the little balls back in the old crank bearings.I'd put them in the bike backwards the first time! Oops. Good thing I had brought all my tools!35mins, and my friend and I were back on the road! Ended the day at 25miles! Insane.

Here is the video:http://www.youtube.com/watch?v=UbXOvRA81jA

Thanks again for the great website. Bikes take on a whole new level when their mystery is gone!

One note brought up by John just reminded me that the right side crank arm has a locking pin that needs to be inserted in the chain ring on re-assembly in order for it to work. John was pretty unlucky and ended up with a broken pin! This is the first time I hear this. Anybody else out there had the same experience?

hey i love ur info but i took my crank off when i was fixing my bike to see if everything was working correctly and both of my crowns were broken into like 5 pieces i replaced them three different times and all of them have broke within the 2 months. what do i do? do u have and guesses on what the problem is?

Either you have bad bearings, a spot on the cone or cup or you have put in the wrong size bearing crown. I would check the surface of both cone and cups for any sign of pitting or scratches, that will kill any bearings.

Your website has been very helpful to me. I just finished converting my bike into a fixed gear. So thanks again. I have a question about one piece cranksets, could I take a one piece and put it on a frame made for a three piece?

Great to hear that you managed to put that bike together. To answer your question, no you can't transfer a one piece to a three piece bottom bracket frame. However, I have seen adapters to put a three piece on a one piece frame.

hi there. i have what ive been told a GT BMX bike. ive taken it apart once to check the bearings to regrease them and basically service it. i noticed the crank is bent a tad but when i ride the bike the chain tension gets hard then loose. i'm just wandering if i were to put it in a vice and try straighten it would it weaken the material or could i do good? also is there ANY way at a "back foot brake wheel" can be disabled from using the foot brake?. If not does anyone know of a place i can find some black plastic "mag" wheels?

Hey Clinton, from what you tell me the chain ring is still usable despite the fact that it's bent, so it can't be so badly bent that a little convincing in a vise shouldn't damage or weaken it. As for the back pedal brake hub, the answer is no for me.